This article applies to:
7.x Email Manager for Outlook
Colligo recommends a maximum number of around 7500 folders and sub-folders within the PST. This number of folders/sub-folders is supported in an environment that has sufficient resources and utilizes folder hierarchies (ie. there is not 7500 folders at the root).
Possible ways to work with document libraries that have more than this number of folders is to add favorites to specific folders, or use the move and copy buttons in the Outlook ribbon and select Other SharePoint Location